| zirkumpolar | circumpolar |
| Zirkular | circular letter |
| zirkumbinär | circumbinary |
| Zirkumflex | circumflex |
| Zirkumfix | circumfix |
| Traumpaar | perfect couple |
| bipolar | bipolar |
| subpolar | subpolar |
| Prämolar | premolar |
| Zirkulieren | circulation |
| zirkulieren | circulate |
| Zirkumzision | circumcision |
| zirka | approximate |
| Zirkel | compass pair of compasses circle |
| Zirkon | zircon |
| Zirkulation | circulation |
| Zirkus | circus |
| zirkadian | circadian |
| Birkenholz | birch wood |
| Birkenpilz | birch bolete rough-stemmed bolete scaber stalk |